WO2022222090A1

WO2022222090A1 - Ink

Info

Publication number: WO2022222090A1
Application number: PCT/CN2021/088911
Authority: WO
Inventors: Jianan Wang; Tomoaki SHINKAI; Ryota Hibino; Cheawchan Sumitra; Shizheng HOU
Original assignee: Dic Corporation
Priority date: 2021-04-22
Filing date: 2021-04-22
Publication date: 2022-10-27
Also published as: JP2023553506A; JP7448097B2; CN117043287A

Abstract

An ink in which a polymer (B) having an aromatic ring structure is dispersed in water (C) by a polymer (A) having a carboxyl group or a functional group in which a carboxyl group is neutralized by some basic compounds. The ink has rub fastness at a level where the printed surface will not be peeled off or rubbed.

Description

INK

Technical Field

The present invention relates to an ink which can be used in various printing methods including, for example, an inkjet printing method.

Background Art

It has been known that an ink containing, for example, a pigment, can be used when printing images of letters, pictures, patterns, or the like on recording media including cloths such as woven fabric, nonwoven fabric, and knitted fabric, plain paper, and coated paper.

With respect to the above-mentioned ink, generally, there has been known an ink which is obtained by mixing a binder resin and other additives into an aqueous pigment dispersion containing a pigment at a high concentration, which is diluted with water as needed. For example, a printing ink, which has a polyurethane resin as a binder resin, used in printing on a cloth has been known (see, for example, Patent Literature 1) .

As a printing method for the ink on a recording medium, for example, a method using an inkjet recording apparatus has been known. The printing method using an inkjet recording apparatus has advantages in that the formation of a printing plate for each picture or pattern to be printed is not needed, and that the cost and the time to delivery in small-size lot printing can be reduced, and thus the use of the method in the production of fiber products, such as clothes and a curtain, is studied.

Usually in the fabric products, printed surfaces may come into contact with each other or the printed surfaces may come into contact with other articles during a printing process or a process of use, or may be washed together with a detergent liquid.

However, in prior art, when the aforementioned contact is repeated, the printed surface may be peeled off or rubbed over time, resulting in poor appearance.

The aforementioned problems such as rubbing can also occur when plain paper or coated paper is used as a recording medium. For example, when the printed surface and a conveying roll come into contact with each other inside a printer, the printed surface may be rubbed, resulting in poor appearance of a printed matter.

In addition, in order to form a clear and highly colored image or the like on the plain paper, coated paper, fabric products or the like, a method of increasing the concentration of a pigment contained in an ink can be mentioned.

However, there has been a problem that an ink having a high pigment concentration tends to cause clogging of a nozzle or an abnormality in the ink discharge direction when discharged by an inkjet printing method.

Citation List

Patent Literature

PTL 1: JP-A-2016-199643

Summary of Invention

Technical Problem

A problem to be solved by the invention is to provide an ink which has rub fastness at a level where the printed surface will not be peeled off or rubbed even when, for example, printed surfaces come into contact with each other or the printed surfaces come into contact with other articles and the like during the printing process on fiber products such as clothing or a recording medium such as plain paper, or during the process of using the printed matter, and has discharge stability at a level that will not cause clogging of an ink nozzle or abnormalities in the ink discharge direction of an inkjet recording apparatus, and also form a printed image or the like having washing fastness at a level where the image will not be removed from a recording medium, such as a cloth, even when, for example, washed with water, warm water, or in a liquid containing a detergent or the like.

Solution to Problem

The inventors of the invention have solved the problems by an ink in which a polymer (B) having an aromatic ring structure is dispersed in water (C) by a polymer (A) having a carboxyl group or a functional group in which a carboxyl group is neutralized by some basic compounds and a structural unit represented by the following general formula (1) .

[Chem. 1]

(M in the general formula (1) represents a hydrogen atom or an alkali metal. ) Advantageous Effects of Invention

The ink of the invention can be used in the production of a printed matter having excellent rub fastness and remarkable washing fastness. Moreover, since the ink has discharge stability at a level that will not cause clogging of an ink nozzle or abnormalities in the ink discharge direction of an inkjet recording apparatus, the ink can be suitably used for inkjet printing on a recording medium such as a cloth.

Description of Embodiments

The ink of the invention is an ink in which a polymer (B) having an aromatic ring structure is dispersed in water (C) by a polymer (A) having a carboxyl group or a functional group in which a carboxyl group is neutralized by some basic compounds and a structural unit represented by the following general formula (1) .

[Chem. 2]

(M in the general formula (1) represents a hydrogen atom or an alkali metal. )

By using the ink of the invention, it is possible to produce a printed matter having excellent rub fastness even when the drying time after printing is short while maintaining good discharge stability of the ink, and having high coloring property when printed on a recording medium such as plain paper. Moreover, the printed matter obtained by using the ink of the invention not only has excellent rub fastness when the drying time after printing is short as described above, but also has further excellent rub fastness by being sufficiently dried. Moreover, by using the ink of the invention, it is possible to produce a printed matter having washing fastness at a very high level while maintaining good discharge stability of the ink even when it is used in printing on a cloth.

The polymer (A) is used to stably disperse the polymer (B) in water (C) . Therefore, unlike a pigment-dispersing resin to be described later, the polymer (A) does not substantially contribute to the improvement of the dispersibility of a pigment to be described later in water (C) .

The polymer (A) and the polymer (B) exist in a form of particles in water (C) . Specifically, the particles of the polymer (A) exist on the surface of the particles of the polymer (B) , thus forming one dispersion (X) . The polymer (A) may be in a state of being adsorbed on the surface of the particles of the polymer (B) . In addition, the polymer (A) may be in a state where a film is formed on the surface of the particles of the polymer (B) .

The dispersed particle size of the dispersion (X) is preferably in the range of 20 nm to 1000 nm, more preferably in the range of 200 nm to 600 nm, and particularly preferably in the range of 240 nm to 500 nm in view of preventing the deterioration of ink discharge stability due to an increase in ink viscosity and, in particular, preventing kogation (a phenomenon in which components contained in ink are adsorbed on heated parts in the head and hinder the generation of bubbles which should have been a driving force for ink discharge) of thermal-type inkjet printing heads. The volume average particle size refers to a value measured by a dynamic light scattering method.

The dispersion (X) containing the polymer (A) and the polymer (B) plays a role as a so-called binder resin. A binder resin is generally used for the purpose of improving the rub fastness and washing fastness of a printed matter. As the binder resin, a binder resin having a volume average particle size of about 5 nm to 20 nm is conventionally used. However, the binder resin having a very small volume average particle size as described above tends to increase the dynamic viscosity of the ink, and as a result, the discharge stability of the ink may be lowered. In order to prevent the dynamic viscosity of the ink from increasing and to maintain good discharge stability of the ink, a method of using an emulsion resin having a relatively large particle size as the binder resin can be mentioned. However, the emulsion resin is usually produced by an emulsion polymerization method using an emulsifier, and thus the emulsion resin contains an emulsifier. The emulsifier may cause the aforementioned kogation.

In the invention, by using an ink in which the polymer (B) is dispersed in water (C) by the polymer (A) , the dispersed particle size of the dispersion (X) is controlled to be larger than that of a conventional one, and thus it is possible to maintain good ink discharge stability and produce a printed matter having excellent rub fastness. Moreover, it is possible to produce a printed matter having washing fastness at a very high level by being used in printing on a cloth. Moreover, since the ink of the invention can reduce the amount of the emulsifier used as described above, the ink has an effect that it is unlikely to cause kogation even when applied to a thermal-type inkjet printing method.

The ink of the invention does not exclude the use of emulsifiers as described above. However, in view of having all of excellent rub fastness, washing fastness and discharge stability and suppressing the occurrence of kogation, the content of the emulsifier is preferably in the range of 0 to 1%by mass, more preferably in the range of 0 to 0.5%by mass, further more preferably in the range of 0 to 0.01%by mass, and particularly preferably 0%by mass, based on the total amount of the ink of the invention.

As the polymer (A) , a polymer having a carboxyl group or a functional group in which a carboxyl group is neutralized by some basic compounds and a structural unit represented by the following general formula (1) is used. The functional group –SO ₃M in the structural unit represented by the general formula (1) represents a sulfonic acid group or a sulfonic acid alkali metal salt group.

[Chem. 3]

(M in the general formula (1) represents a hydrogen atom or an alkali metal. )

For example, a polymer obtained by radical polymerization of a monomer having a polymerizable unsaturated double bond may be used as the polymer (A) .

As the monomer, a vinyl monomer having a carboxyl group for introducing a carboxyl group into the polymer (A) and a vinyl monomer for introducing the structure represented by the general formula (1) into the polymer (A) may be used in combination, with other vinyl monomers as needed.

As the vinyl monomer having a carboxyl group, for example, acrylic acid, methacrylic acid, β-carboxyethyl (meth) acrylate, 2- (meth) acryloyl propionic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, itaconic acid half ester, maleic acid half ester, β- (meth) acryloyloxyethyl hydrogen succinate, β- (meth) hydroxyethyl hydrogen phthalate, salts thereof, and acid anhydrides such as maleic anhydride may be used alone or in combination of two or more. Among them, it is preferable to use acrylic acid and methacrylic acid in view of obtaining a printed matter having excellent rub fastness and having high coloring property when printed on a recording medium such as plain paper.

The vinyl monomer having a carboxyl group is preferably used, based on the total amount of the monomers used in the production of the polymer (A) , in the range of 1%by mass to 80%by mass, more preferably in the range of 5%by mass to 70%by mass, and is preferably used in the range of 10 to 50%by mass in view of obtaining an ink capable of producing a printed matter having all of more excellent rub fastness, washing fastness and coloring property.

Further, as the vinyl monomer for introducing the structural unit represented by the general formula (1) into the polymer (A) , for example, styrene sulfonic acid, an alkali metal salt of styrene sulfonic acid, or the like may be used. As the alkali metal salt of styrene sulfonic acid, a sodium styrene sulfonate, a lithium styrene sulfonate, or the like may be used. Among them, it is particularly preferable to use a sodium styrene sulfonate in view of obtaining an ink capable of producing a printed matter having excellent rub fastness.

The vinyl monomer for introducing the structural unit represented by the general formula (1) into the polymer (A) is preferably used, based on the total amount of the monomers used in the production of the polymer (A) , in the range of 1%by mass to 90%by mass, and is preferably used in the range of 40 to 90%by mass in view of obtaining an ink capable of producing a printed matter having both more excellent rub fastness and coloring property.

As the other monomers that can be used in the production of the polymer (A) , for example, a monomer having a phosphorus atom may be used.

Examples of the monomer having a phosphorus atom include 2- (meth) acryloyloxyethyl acid phosphate (for example, “Light Ester P-1M” , “Light Acrylate P-1A” , etc. manufactured by Kyoeisha Chemical Co., Ltd. ) , bis (2- (meth) acryloyloxyethyl) acid phosphate, phosphate ester of polyalkylene glycol mono (meth) acrylate such as phosphate ester of polyethylene glycol monomethacrylate (for example, “Sipomer PAM100” , “Sipomer PAM4000” , etc. manufactured by Rhodia Nicca, Ltd. ) , phosphate ester of polyethylene glycol monoacrylate (for example, “Sipomer PAM5000” , etc. manufactured by Rhodia Nicca, Ltd. ) , phosphate ester of polypropylene glycol monomethacrylate (for example, “Sipomer PAM200” , etc. manufactured by Rhodia Nicca, Ltd. ) , and phosphate ester of polypropylene glycol monoacrylate (for example, “Sipomer PAM300” etc. manufactured by Rhodia Nicca, Ltd. ) , alkylene phosphate (meth) acrylate such as methylene phosphate (meth) acrylate, trimethylene phosphate (meth) acrylate, propylene phosphate (meth) acrylate, and tetramethylene phosphate (meth) acrylate, etc.

Further, examples of the other monomers include (meth) acrylic acid esters such as methyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, phenyl (meth) acrylate, and benzyl (meth) acrylate; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl versatate; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, amyl vinyl ether, and hexyl vinyl ether; vinyl-based nitriles such as (meth) acrylonitrile; vinyl-based monomers having an aromatic ring such as styrene, α-methylstyrene, vinyltoluene, vinylanisol, α-halostyrene, vinyl naphthalene, and divinylstyrene; glycidyl group-containing vinyl-based monomers such as glycidyl (meth) acrylate and allyl glycidyl ether; hydroxyl group-containing vinyl-based monomers such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, and glycerol mono (meth) acrylate; vinyl-based monomers containing a methylolamide group or an alkoxylated product thereof, such as N-methylol (meth) acrylamide, N-isopropoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, and N-isobutoxymethyl (meth) acrylamide; amide group-containing vinyl-based monomers such as (meth) acrylamide, N-monoalkyl (meth) acrylamide, and N, N-dialkyl (meth) acrylamide, etc. These may be used alone or in combination of two or more.

The polymer (A) may be produced by, for example, supplying a mixture of the aforementioned vinyl monomers in a lump or in a divided manner in the presence of water (C) or, when necessary, a polymerization initiator or a chain transfer agent, and subjecting the mixture to radical polymerization.

Examples of the polymerization initiator include persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate, peroxides such as benzoyl peroxide, cumene hydroperoxide, and t-butyl hydroperoxide, hydrogen peroxide, redox polymerization initiators combining the aforementioned peroxide and a reducing agent, azo-based initiators such as 4, 4’-azobis (4-cyanovaleric acid) and 2, 2’-azobis (2-amidinopropane) dihydrochloride, etc. Examples of the reducing agent include ascorbic acid, erythorbic acid, sodium erythorbate, a metal salt of formaldehyde sulfoxylate, sodium thiosulfate, and sodium bisulfite.

Among them, the ammonium persulfate is preferably used as the polymerization initiator in view of improving the production efficiency of the polymer (A) .

Examples of the chain transfer agent include thiomalic acid, thioglycerin and the like, and these may be used alone or in combination of two or more. It is preferable to use thiomalic acid in view of obtaining an ink capable of producing a printed matter having excellent dispersion stability and excellent coloring property.

The production of the polymer (A) is usually preferably carried out in a temperature of 30℃ to 100℃ for 1 hour to 40 hours. The polymer (A) is preferably produced in the presence of an inert gas such as nitrogen gas in order to promptly polymerize the vinyl monomers.

The polymer (A) may be neutralized by mixing with some basic compounds as a neutralizing agent, when necessary, after the polymerization of the monomers.

Examples of the basic compound include alkali metal compounds such as sodium hydroxide and potassium hydroxide; alkaline earth metal compounds such as calcium hydroxide and calcium carbonate; ammonia; organic amines such as monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monopropylamine, dimethylpropylamine, monoethanolamine, diethanolamine, dimethylethanolamine, triethanolamine, ethylenediamine, and diethylenetriamine, etc. These may be used alone or in combination of two or more, and it is preferable to use ammonia or aqueous ammonia in view of obtaining an ink capable of producing a printed matter having excellent dispersion stability and excellent coloring property.

A composition in which the polymer (A) is dissolved or dispersed in water (C) can be produced by the above method.

As the polymer (A) obtained by the above method, it is preferable to use a polymer having a weight average molecular weight of 1000 to 20000, and it is preferable to use a polymer having a weight average molecular weight of 3000 to 15000 in view of obtaining an ink capable of producing a printed matter having all of more excellent rub fastness, washing fastness and coloring property.

Next, the polymer (B) included in the ink of the invention will be described.

As the polymer (B) , a polymer having an aromatic ring structure is used. As a result, a printed matter obtained by using the ink of the invention can be imparted with excellent rub fastness. In particular, it is possible to dramatically improve washing fastness of a printed matter obtained by printing on a cloth using the ink of the invention.

As the polymer (B) , the aromatic ring structure is used preferably in the range of 5%by mass to 70%by mass, more preferably in the range of 10%by mass to 50%by mass based on the total amount of the polymer (B) , and the aromatic ring structure in the range of 10%by mass to 40%by mass is preferably used in view of obtaining a printed matter having more excellent washing fastness and rub fastness.

As the aromatic ring structure, for example, a structure derived from styrene or the like can be mentioned. Among them, a structure derived from styrene is preferred in view of obtaining a printed matter having washing fastness at a very high level.

The polymer (B) preferably contains the structure represented by the following general formula (2) , based on the total amount of the polymer (B) , in the range of 30%by mass to 90%by mass, more preferably in the range of 40%by mass to 80%by mass, and preferably in the range of 40%by mass to 70%by mass in view of obtaining a printed matter having more excellent washing fastness and rub fastness.

[Chem. 4]

(R ¹ and R ² in the general formula (2) represents a alkyl group having 2 to 5 carbon atoms. )

Examples of the polymer (B) include various polymers such as a vinyl polymer (b) , polyurethane, and polyester. Among them, it is preferable to use the vinyl polymer (b) as the polymer (B) .

As the vinyl polymer (b) , a polymer of vinyl monomers such as styrene, or (meth) acrylic monomers or the like can be used.

As the vinyl monomer, styrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, vinylpyrene, vinyltoluene or the like can be used for introducing the aromatic ring structure into the polymer (B) . Styrene is preferably used in view of obtaining a printed matter having washing fastness at a very high level.

As the (meth) acrylic monomer, it is preferable to use ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, hexyl (meth) acrylate in view of introducing the structural unit represented by the general formula (2) into the polymer (B) .

As the (meth) acrylic monomer, in addition to the ethyl (meth) acrylate or the like, other vinyl monomers may be used as needed, and examples thereof include (meth) acrylic acid esters such as methyl (meth) acrylate, cyclohexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, phenyl (meth) acrylate, and benzyl (meth) acrylate, and vinyl monomers having a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate.

The vinyl polymer (b) can be produced by polymerizing a mixture of vinyl monomers containing the ethyl (meth) acrylate.

On the other hand, the ink of the invention is an ink in which the polymer (B) is dispersed in water (C) by the polymer (A) . Therefore, the polymer (B) is preferably produced in the presence of the polymer (A) in view of obtaining an ink capable of producing a printed matter having excellent dispersion stability and excellent rub fastness.

Specifically, examples of a method for producing the polymer (B) include a method of supplying an (meth) acrylic monomer or the like included in the vinyl polymer (b) in a lump or in a divided manner to a composition in which the polymer (A) is dissolved or dispersed in water (C) , and subjecting the mixture to polymerization.

According to the above method, it is possible to obtain a composition in which the polymer (B) is dispersed in water (C) by the polymer (A) , and it is possible to use the composition for the ink of the invention.

In addition, the ink of the invention preferably contains the polymer (A) and the polymer (B) in a total amount, based on the total amount of the ink, in the range of 0.1%by mass to 30%by mass, more preferably in the range of 0.1%by mass to 20%by mass, and particularly preferably in the range of 0.5%by mass to 10%by mass in view of obtaining an ink capable of producing a printed matter having more excellent rub fastness.

In the ink of the invention obtained by the above method, the mass ratio of the polymer (A) to the polymer (B) [polymer (A) /polymer (B) ] is preferably in the range of 1/100 to 30/100, and more preferably in the range of 1/100 to 20/100 in view of obtaining an ink capable of producing a printed matter having more excellent rub fastness.

As the water (C) , pure water such as ion-exchanged water, ultra-filtered water, reverse-osmosed membrane treated water, and distilled water, or ultrapure water can be used. In addition, as the water, water sterilized by irradiation with ultraviolet rays or by addition of hydrogen peroxide or the like is preferably used because it is possible to prevent the generation of fungi or bacteria when the ink of the invention is stored for a long period of time.

Based on the total amount of the ink of the invention, the water (C) is preferably contained in the range of 40%by mass to 95%by mass, and more preferably contained in the range of 50%by mass to 90%by mass in view of obtaining an ink capable of producing a printed matter having both more excellent rub fastness and coloring property.

An ink containing, in addition to the polymer (A) , the polymer (B) , and water (C) , other components as needed can be used as the ink of the invention.

Examples of the other components include a coloring material such as a pigment and a dye, a pigment-dispersing resin, a binder resin other than the polymer (A) and the polymer (B) , a solvent other than the water (C) , a wetting agent, a lubricant, an alkaline agent, a pH adjustor, a surfactant, an antiseptic agent, a chelating agent, a plasticizer, an antioxidant, a wax, an ultraviolet light absorber, and the like. Among them, as the other components, it is preferable to use, as a binder resin other than the polymer (A) and the polymer (B) , a vinyl-based copolymer having an anionic group, such as the polyester resin having an anionic group, an epoxy resin having an anionic group, a urethane resin having an anionic group, an acrylic acid resin having an anionic group, a maleic acid resin having an anionic group, a styrene resin having an anionic group, and a polyvinyl acetic acid-based resin having an anionic group. Among them, it is particularly preferable to use a urethane resin having an anionic group in view of obtaining an ink capable of producing a printed matter having more excellent rub fastness and washing fastness.

As the pigment, for example, an organic pigment or an inorganic pigment can be used alone or in combination of two or more.

Examples of the organic pigment include quinacridone pigments, quinacridone quinone pigments, dioxazine pigments, phthalocyanine pigments, phthalone pigments, isoindolinone pigments, methane/azomethine pigments, azo pigments, disazo pigments, anthrapymidin pigments, anthanthrone pigments, indanthrone pigments, flavanthrone pigments, perylene pigments, diketopyrrolopyrrole pigments, perinone pigments, quinophthalone pigments, anthraquinone pigments, thioindigo pigments, benzimidazolone pigments, azo lake pigments, insoluble azo pigments, condensed azo pigments, etc.

Examples of the inorganic pigment include titanium dioxide, zinc oxide, iron oxide, chromium oxide, iron black, cobalt blue, alumina white, iron oxide yellow, viridian, zinc sulfide, lithobon, cadmium yellow, vermilion, cadmium red, chrome yellow, molybdate orange, zinc chromate, strontium chromate, white carbon, clay, talc, ultramarine, precipitated barium sulfate, barite powder, calcium carbonate, white lead, dark blue, manganese violet, carbon black, aluminum powder, pearl pigments, etc.

A pigment which can be self-dispersed in water can also be used as the pigment.

The pigment is preferably used, based on the total amount of the ink, in the range of 0.1%by mass to 20%by mass, and more preferably used in the range of 1%by mass to 10%by mass in view of obtaining an ink having excellent storage stability and having excellent discharge stability when applied to an inkjet printing method.

When the pigment is used as the coloring material, it is preferable to use a pigment-dispersing resin in order to stably disperse the pigment in the water (C) . Unlike the polymer (A) or the polymer (B) , the pigment-dispersing resin imparts dispersion stability to the pigment in water (C) by adsorbing around the particles of the pigment.

As the pigment-dispersing resin, for example, a pigment-dispersing resin having an anionic group can be used. Examples of the anionic group include a carboxyl group, a sulfonate group, a phosphate group, etc.

It is particularly preferable to use a resin having a hydrophobic structural unit and a hydrophilic structural unit derived from an anionic group as the pigment-dispersing resin having an anionic group in view of obtaining an ink having a high degree of freedom in designing a structure that maintains the stability of the ink of the invention and capable of forming a printed matter having excellent coloring property when printed on plain paper.

As the resin having a hydrophobic structural unit and a hydrophilic structural unit derived from an anionic group, for example, the pigment-dispersing resin can use a resin having a structural unit derived from styrene and a structural unit derived from acrylic acid.

As the resin having a hydrophobic structural unit and a hydrophilic structural unit derived from an anionic group, it is preferable to use a resin having an acid value in the range of 60 to 300 mgKOH/g, and suitable in the range of 100 to 250 mgKOH/g in view of balancing pigment dispersibility, ink stability, and high print density.

In view of balancing the pigment dispersibility in water (C) , ink stability, rub fastness, washing fastness, high print density, and further discharge property, as the resin having a hydrophobic structural unit and a hydrophilic structural unit derived from an anionic group, it is preferable to use a resin having a weight average molecular weight in the range of 3000 to 50000, more preferably in the range of 4000 to 40000, further more preferably in the range of 5000 to 30000, and particularly preferably in the range of 5000 to 20000.

In view of maintaining excellent discharge stability without deteriorating the resin due to the influence of heat from the thermal jet method even when the ink of the invention is applied to a thermal-jet inkjet printing method, it is preferable to use a resin having a glass transition temperature in the range of 30℃ to 150℃, more preferable in the range of 70℃ to 150℃, as the resin having a hydrophobic structural unit and a hydrophilic structural unit derived from an anionic group.

The resin having a hydrophobic structural unit and a hydrophilic structural unit derived from an anionic group is preferably a resin that can have water dispersibility by neutralizing the anionic group, and preferably a resin that has the ability to form stable aqueous dispersion particles under the action of some basic compounds serving as a neutralizing agent without using a dispersion stabilizer such as an emulsifier.

When a resin having an anionic group is used as the pigment-dispersing resin, an inorganic basic compound or an organic basic compound may be used as the basic compound that can be used for neutralizing the anionic group. It is preferable to use an inorganic basic compound as the basic compound in view of obtaining an ink having more excellent storage stability.

As the inorganic basic compound, alkali metal hydroxides, ammonium hydroxides and the like can be used, and alkali metal hydroxides such as potassium hydroxides and sodium hydroxides are preferably used in view of imparting the pigment with more excellent dispersion stability. In view of improving miscibility, an aqueous solution in which the inorganic basic compound has been previously dissolved or dispersed in water with a concentration of 10%by mass to 60%by mass can be used.

Further, examples of the organic basic compound include amines such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, diethanolamine, and triethanolamine. These amines are generally in a liquid state, and thus can be used as they are.

It is preferable to adjust the content of the basic compound such that the neutralization rate of the resin having an anionic group is preferably 50%or more, more preferably 70%or more, in view of improving the dispersion rate in water (C) and ensuring good dispersion stability and long-term storage stability. The upper limit of the neutralization rate is not particularly limited; however, it is preferably 200%or less, more preferably 120%or less so that, substantially, the ink is stable and does not gel even when stored for a long period of time. Here, the neutralization rate refers to a value calculated by the following formula.

Neutralization rate (%) = [ {mass of basic compound (g) × 56.11 ×1000} / {acid value of pigment-dispersing resin (mgKOH/g) × equivalent of basic compound × mass of pigment-dispersing resin (g) } ] × 100

More specifically, as the pigment-dispersing resin, for example, a vinyl-based copolymer having an anionic group such as the polyester resin having an anionic group, an epoxy resin having an anionic group, a urethane resin having an anionic group, an acrylic acid resin having an anionic group, a maleic acid resin having an anionic group, a styrene resin having an anionic group, and a polyvinyl acetic acid-based resin having an anionic group can be used.

Examples of the pigment-dispersing resin include poly (meth) acrylic acid, vinyl acetate-acrylic acid ester copolymers, acrylic acid-acrylic acid alkyl ester copolymers, styrene- (meth) acrylic acid copolymers, styrene- (meth) acrylic acid-acrylic acid alkyl ester copolymers, styrene-maleic acid copolymers, vinyl acetate-maleic acid ester copolymers, vinyl acetate-crotonic acid copolymers, and vinyl acetate-acrylic acid copolymers.

Examples of the wetting agent include ethers of polyhydric alcohols such as ethylene glycol and glycerol, ethers of polyhydric alcohols such as ethylene glycol monoethyl ether and ethylene glycol monobutyl ether; polyoxyalkylene adducts of glycerin; nitrogen-containing heterocyclic compounds such as N-methyl-2-pyrrolidone and γ-butyrolactone; amides such as N, N-dimethylformamide; organic amines such as triethylamine, sulfur-containing compounds such as dimethyl sulfoxide, propylene carbonate, ethylene carbonate, etc., and these may be used alone or in combination of two or more.

As the wetting agent, it is preferable to use a wetting agent having a high boiling point in order to uniformly disperse the pigment and the pigment-dispersing resin, and it is more preferable to use polyhydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, glycerin, and polyethylene oxide adduct of glycerin.

The wetting agent is preferably used in the range of 10%by mass to 1000%by mass, more preferably 30%by mass to 200%by mass, based on the total amount of the pigment.

When an ink containing the pigment and the pigment-dispersing resin is used as the ink of the invention, as a method for producing the ink of the invention, for example, a production method of mixing an aqueous pigment dispersion obtained by mixing the pigment, the pigment-dispersing resin, and water (C) in advance, with a composition containing the polymer (A) , the polymer (B) , and water (C) can be mentioned.

The aqueous pigment dispersion can be produced by going through, for example, a step [1] of kneading a composition containing the pigment, the pigment-dispersing resin, and some basic compounds or a wetting agent as needed, and a step [2] of diluting and dispersing the kneaded product obtained in step [1] in water (C) , etc.

By appropriately selecting the pigment-dispersing resin in the steps [1] and [2] , the affinity of the pigment-dispersing resin with the pigment becomes extremely good, the dispersion stability of the aqueous pigment dispersion is improved, and it is possible to improve the gloss, durability, water resistance and the like of a printed matter formed by printing the ink obtained by using the pigment dispersion on a recording medium.

In the step [1] , for example, an apparatus such as a roll mill, a Henschel mixer, a pressure kneader, and a planetary mixer can be used. An apparatus such as a Henschel mixer, a pressure kneader, and a planetary mixer which has a stirring tank that can be sealed and stirring blades is preferably used because it is possible to keep the solid content ratio of the composition in the step [1] constant and obtain a kneaded product having a good dispersed state. A planetary mixer is preferably used because the kneading treatment can be performed in a wide range of viscosity regions.

Further, the step [2] is a step of diluting and dispersing the kneaded product obtained in the step [1] in water (C) .

The aqueous pigment dispersion obtained by the above method is preferably subjected to a centrifugal separation treatment or a filtration treatment to remove coarse particles or agglomerated particles derived from raw materials of the pigment and the like, in view of preventing the occurrence of clogging of the ink nozzle when the ink of the invention is applied to an inkjet printing method.

For the ink of the invention, there can be mentioned a method of mixing the aqueous pigment dispersion obtained by the above method and a composition in which the polymer (B) is dispersed in water (C) by the polymer (A) and stirring for 30 to 90 minutes, etc.

As the ink of the invention obtained by the above method, for example, it is preferable to use an ink having a viscosity in the range of 1 mPa·sec to 10 mPa·sec. In particular, it is more preferable to use an ink having a viscosity of 1 mPa·sec to 6 mPa·sec in the case where the ink of the invention is discharged by an inkjet printing method which will be described later.

The ink of the invention can be used for printing on a recording medium.

Examples of the recording medium include coated paper having an ink absorbing layer which easily absorbs the ink solvent and fixes pigments and the like on the surface, coated paper provided with a layer that does not easily absorb the ink solvent, plain paper, cloth, etc.

By the way, when an inkjet printer capable of duplex printing is used for printing on a recording medium, usually a single-sided printed matter with on one side (front side) of the recording medium printed is dried for a certain period of time, and is then inverted by a conveying roll and a reversing mechanism inside the printer to have the other side (back side) of the single-sided printed matter printed. When inverting the single-sided printed matter, as the conveying roll or the like comes into contact with the printed side of the single-sided printed matter, the printed side may be scratched, causing deterioration of print quality. In particular, when duplex printing is performed on coated paper, which is less likely to absorb the solvent in the ink as compared with plain paper, there is a concern that the print quality may be deteriorated.

However, the ink of the invention is excellent in rub fastness even in duplex printing on coat paper or plain paper, and thus it is not easily scratched, and further, it is possible to effectively prevent a deterioration in coloring property when printed on plain paper.

The ink of the invention can be suitably used for printing using a cloth as the recording medium. There is a tendency that the polymer (B) dispersed in water (C) by the polymer (A) contained in the ink of the invention has a high affinity with fibers constituting the cloth due to the influence of the aromatic ring structure. Thus, in the printed matter obtained by printing the ink of the invention on a cloth, the ink does not easily come off from the cloth even when the printed matter is washed with water, warm water, or a detergent liquid, and it is possible to maintain a printed image having a high color density even after washing. On the other hand, since the ink having high affinity with the cloth is always slightly hydrophobic, it is sometimes not suitable for inkjet printing method. However, the ink of the invention can be used to produce a printed matter having washing fastness at a very high level without compromising the excellent discharge stability even when inkjet printing method is used.

As described above, the printed matter printed using the ink of the invention can have both excellent rub fastness, washing fastness and high coloring property.

Although the ink of the invention can be applied to various printing methods, it can be suitably used exclusively for printing by an inkjet printing method.

Examples of the inkjet printing method include a continuous injection type (a charge control type, a spray type, etc. ) , an on-demand type (a piezo method, a thermal method, an electrostatic suction method, etc. ) , etc., and the ink of the invention is suitable for printing by a thermal type inkjet printing method. When applied to these various inkjet methods, this water-based ink for inkjet recording basically enables extremely stable ink discharge, and further, can achieve excellent scratch resistance and rub fastness of a formed image.

Examples

[Synthetic Example 1]

138 parts by mass of deionized water was put in a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen introduction tube, a thermometer, and a dropping funnel, and the temperature was raised to 80℃ while blowing nitrogen into the reaction vessel.

Next, 4.51 parts by mass of a methacrylic acid, 5.63 parts by mass of a sodium styrene sulfonate, and 0.15 parts by mass of a thiomalic acid were added and heated by 80℃, and 5 parts by mass of a 10 mass%ammonium persulfate aqueous solution was added to initiate polymerization.

After maintaining the temperature in the polymerization vessel at 80℃ for 1 hour, the contents in the polymerization vessel were cooled to 40℃ or lower and mixed with aqueous ammonia to obtain an aqueous solution (I-1) of a polymer (A-1) .

Then, 100 parts by mass of a mixture forming a polymer (B-1) including 65 parts by mass of ethyl acrylate, 5 parts by mass of styrene, and 30 parts by mass of 2-hydroxyethyl methacrylate, and 5 parts by mass of a 10 mass%ammonium persulfate aqueous solution were added dropwise for 4 hours to the aqueous solution (I-1) of the polymer (A-1) which had been adjusted to 80℃, and were maintained for 1 hour to allow polymerization.

After the aforementioned 1 hour elapsed, the contents in the reaction vessel were cooled to 40℃ or lower.

After the cooling, aqueous ammonia was supplied to the reaction vessel to adjust the pH of the contents to 7, and the reaction vessel was mixed for 1 hour, so that a dispersion (II-1) having a non-volatile content of 40%by mass in which the polymer (B-1) was dispersed in water by the polymer (A-1) was obtained. The volume average particle size of dispersing elements contained in the dispersion (II-1) was 350 nm.

The volume average particle size was calculated using NANOTRAC WAVE II manufactured by MicrotracBEL Corp. First, the dispersion was diluted 1000 times with ion-exchanged water. Then, approximately 4 ml of the diluted dispersion was placed in a cell, and the volume average particle size (MV) was measured by detecting scattered light of laser light in an environment of 25℃ using the NANOTRAC WAVE II manufactured by MicrotracBEL Corp. The volume average particle size was measured three times to calculate an average value (integer) . The value obtained by truncating the first digit of the average value was taken as the value of the volume average particle size (unit: nm) .

[Synthetic Example 2]

A dispersion (II-2) having a non-volatile content of 40%by mass in which a polymer (B-2) was dispersed in water by a polymer (A-2) was obtained by the same method as in Synthetic Example 1 except that 65 parts by mass of ethyl acrylate was changed to 65 parts by mass of n-butyl acrylate. The volume average particle size of dispersing elements contained in the dispersion (II-2) was 310 nm.

[Synthetic Example 3]

A dispersion (II-3) having a non-volatile content of 40%by mass in which a polymer (B-3) was dispersed in water by a polymer (A-3) was obtained by the same method as in Synthetic Example 1 except that 65 parts by mass of ethyl acrylate was changed to 65 parts by mass of isobutyl acrylate. The volume average particle size of dispersing elements contained in the dispersion (II-3) was 320 nm.

[Synthetic Example 4]

A dispersion (II-4) having a non-volatile content of 40%by mass in which a polymer (B-4) was dispersed in water by a polymer (A-4) was obtained by the same method as in Synthetic Example 1 except that the amount of ethyl acrylate used was changed from 65 parts by mass to 40 parts by mass and the amount of styrene used was changed from 5 parts by mass to 30 parts by mass. The volume average particle size of dispersing elements contained in the dispersion (II-4) was 370 nm.

[Synthetic Example 5]

A dispersion (II-5) having a non-volatile content of 40%by mass in which a polymer (B-5) was dispersed in water by a polymer (A-5) was obtained by the same method as in Synthetic Example 1 except that the amount of ethyl acrylate used was changed from 65 parts by mass to 40 parts by mass, the amount of styrene used was changed from 5 parts by mass to 30 parts by mass, and aqueous potassium hydroxide solution was used instead of aqueous ammonia to adjust the pH to 7. The volume average particle size of dispersing elements contained in the dispersion (II-5) was 340 nm.

[Synthetic Example 6]

A dispersion (II-6) having a non-volatile content of 40%by mass in which a polymer (B-6) was dispersed in water by a polymer (A-6) was obtained by the same method as in Synthetic Example 1 except that the amount of methacrylic acid used was changed from 4.51 parts by mass to 1.03 parts by mass, 65 parts by mass of ethyl acrylate was changed to 71 parts by mass of n-butyl acrylate, the amount of styrene used was changed from 5 parts by mass to 19 parts by mass, and the amount of 2-hydroxyethyl methacrylate used was changed from 30 parts by mass to 10 parts by mass. The volume average particle size of dispersing elements contained in the dispersion (II-6) was 340 nm.

[Synthetic Example 7]

A dispersion (II-7) having a non-volatile content of 40%by mass in which a polymer (B-7) was dispersed in water by a polymer (A-7) was obtained by the same method as in Synthetic Example 1 except that 65 parts by mass of ethyl acrylate was changed to 71 parts by mass of n-butyl acrylate, the amount of styrene used was changed from 5 parts by mass to 19 parts by mass, and the amount of 2-hydroxyethyl methacrylate used was changed from 30 parts by mass to 10 parts by mass. The volume average particle size of dispersing elements contained in the dispersion (II-7) was 380 nm.

[Synthetic Example 8]

A dispersion (II-8) having a non-volatile content of 40%by mass in which a polymer (B-8) was dispersed in water by a polymer (A-8) was obtained by the same method as in Synthetic Example 1 except that the amount of methacrylic acid used was changed from 4.51 parts by mass to 1.03 parts by mass, the amount of ethyl acrylate used was changed from 65 parts by mass to 68 parts by mass, the amount of styrene used was changed from 5 parts by mass to 12 parts by mass, and the amount of 2-hydroxyethyl methacrylate used was changed from 30 parts by mass to 20 parts by mass. The volume average particle size of dispersing elements contained in the dispersion (II-8) was 310 nm.

[Synthetic Example 9]

A dispersion (II-9) having a non-volatile content of 40%by mass in which a polymer (B-9) was dispersed in water by a polymer (A-9) was obtained by the same method as in Synthetic Example 1 except that the amount of methacrylic acid used was changed from 4.51 parts by mass to 1.03 parts by mass, the amount of ethyl acrylate used was changed from 65 parts by mass to 68 parts by mass, the amount of styrene used was changed from 5 parts by mass to 12 parts by mass, and 30 parts by mass of 2-hydroxyethyl methacrylate was changed to 20 parts by mass of 3-hydroxypropyl methacrylate. The volume average particle size of dispersing elements contained in the dispersion (II-9) was 400 nm.

[Synthetic Example 10]

A dispersion (II-10) having a non-volatile content of 40%by mass in which a polymer (B-10) was dispersed in water by a polymer (A-10) was obtained by the same method as in Synthetic Example 1 except that the amount of methacrylic acid used was changed from 4.51 parts by mass to 1.03 parts by mass, 65 parts by mass of ethyl acrylate was changed to 47 parts by mass of n-butyl acrylate, and the amount of styrene used was changed from 5 parts by mass to 23 parts by mass. The volume average particle size of dispersing elements contained in the dispersion (II-10) was 280 nm.

[Table 1]

[Synthetic Example 11]

A dispersion (II-11) having a non-volatile content of 40%by mass in which a polymer (B-11) was dispersed in water by a polymer (A-11) was obtained by the same method as in Synthetic Example 1 except that 5 parts by mass of styrene was changed to 5 parts by mass of methyl methacrylate. The volume average particle size of dispersing elements contained in the dispersion (II-11) was 470nm.

[Synthetic Example 12]

A dispersion (II-12) having a non-volatile content of 40%by mass in which a polymer (B-12) was dispersed in water by a polymer (A-12) was obtained by the same method as in Synthetic Example 11 except that the amount of methacrylic acid used was changed from 4.51 parts by mass to 1.03 parts by mass, the amount of ethyl acrylate used was changed from 65 parts by mass to 68 parts by mass, the amount of methyl methacrylate used was changed from 5 parts by mass to 12 parts by mass, and the amount of 2-hydroxyethyl methacrylate used was changed from 30 parts by mass to 20 parts by mass. The volume average particle size of dispersing elements contained in the dispersion (II-12) was 320 nm.

[Synthetic Example 13]

A dispersion (II-13) having a non-volatile content of 40%by mass in which a polymer (B-13) was dispersed in water by a polymer (A-13) was obtained by the same method as in Synthetic Example 11 except that the amount of methacrylic acid used was changed from 4.51 parts by mass to 1.03 parts by mass, the amount of ethyl acrylate used was changed from 65 parts by mass to 71 parts by mass, the amount of methyl methacrylate used was changed from 5 parts by mass to 19 parts by mass, and the amount of 2-hydroxyethyl methacrylate used was changed from 30 parts by mass to 10 parts by mass. The volume average particle size of dispersing elements contained in the dispersion (II-13) was 290 nm.

[Synthetic Example 14]

A dispersion (II-14) having a non-volatile content of 40%by mass in which a polymer (B-14) was dispersed in water by a polymer (A-14) was obtained by the same method as in Synthetic Example 11 except that the amount of methacrylic acid used was changed from 4.51 parts by mass to 1.03 parts by mass, and the pH was adjusted to 7 using an aqueous potassium hydroxide solution instead of using aqueous ammonia. The volume average particle size of dispersing elements contained in the dispersion (II-14) was 440 nm.

[Synthetic Example 15]

A dispersion (II-15) having a non-volatile content of 40%by mass in which a polymer (B-15) was dispersed in water by a polymer (A-15) was obtained by the same method as in Synthetic Example 11 except that the amount of ethyl acrylate used was changed from 65 parts by mass to 40 parts by mass, and the amount of methyl methacrylate used was changed from 5 parts by mass to 30 parts by mass. The volume average particle size of dispersing elements contained in the dispersion (II-15) was 390 nm.

[Synthetic Example 16]

A dispersion (II-16) having a non-volatile content of 40%by mass in which a polymer (B-16) was dispersed in water by a polymer (A-16) was obtained by the same method as in Synthetic Example 11 except that the amount of methacrylic acid used was changed from 4.51 parts by mass to 1.03 parts by mass, the amount of ethyl acrylate used was changed from 65 parts by mass to 47 parts by mass, and the amount of methyl methacrylate used was changed from 5 parts by mass to 23 parts by mass. The volume average particle size of dispersing elements contained in the dispersion (II-16) was 350 nm.

[Table 2]

[Synthetic Example 17]

250.0 parts by mass of polytetramethylene ether glycol (average molecular weight 1000) and 181.7 parts by mass of hydrogenated 4, 4’-diphenylmethane diisocyanate (H12MDI) were put into a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen introduction tube, and were sufficiently stirred and then reacted at 100℃ for 2 hours. Then, the mixture was cooled to 50℃, 59.3 parts by mass of 2, 2-dimethylolpropionic acid (DMPA) , 122.8 parts by mass of methyl ethyl ketone (MEK) , and 0.18 parts by mass of dibutyltin dilaurylate were added and reacted at 75℃ for 15 hours. After the reaction, the mixture was cooled to 50℃ or lower, added with 204.6 parts by mass of MEK and was stirred for 1 hour while being cooled to 40℃ or lower to obtain a MEK solution of urethane polymer (A-17) . 94.4 parts by mass of a 25 mass%aqueous potassium hydroxide solution was added to the obtained MEK solution of urethane polymer (A-17) , and the mixture was stirred for 30 minutes to neutralize the acid groups. Next, ion-exchanged water was gradually added under strong stirring, and after urethane was emulsified, MEK was distilled by vacuum distillation to obtain a dispersion (II-17) of a polymer (A-17) having a non-volatile content of 40%by mass and an acid value of 50 mgKOH/g. The volume average particle size of dispersing elements contained in the dispersion (II-17) was 15 nm.

[Synthetic Example 18]

A dispersion (II-18) of a polymer (A-18) having a non-volatile content of 40%by mass and an acid value of 25 mgKOH/g was obtained by the same method as in Synthetic Example 17 except that the amount of H12MDI used was changed from 181.7 parts by mass to 111.0 parts by mass, the amount of DMPA used was changed from 59.3 parts by mass to 23.2 parts by mass, and the amount of the 25 mass%aqueous potassium hydroxide solution used was changed from 94.4 parts by mass to 36.8 parts by mass. The volume average particle size of dispersing elements contained in the dispersion (II-18) was 5 nm.

[Example 1]

500 parts by mass of JONCRYL PDX-6137A (manufactured by BASF SE, a styrene acrylic resin aqueous solution having a weight average molecular weight of 16,000, an acid value of 220 to 250, a glass transition point of 100℃, pH 7.8, and a non-volatile content of about 29%by mass) serving as a pigment-dispersing resin and 5000 parts by mass of a magenta pigment (FASTOGEN Super Magenta RY, manufactured by DIC Corporation) were put into a planetary mixer (manufactured by INOUE MFG., INC. ) having a capacity of 50 L, and the jacket was heated.

After the temperature of the contents in the planetary mixer reached 60℃, the contents were stirred and mixed under the conditions of a rotation speed of 80 rotations/minute and a revolution rotation speed of 25 rotations/minute.

After 5 minutes from the start of the stirring, 3, 700 parts by mass of triethylene glycol was added.

Thereafter, a kneaded product was obtained by continuing mixing until 120 minutes had elapsed counting from the time when the current value of the planetary mixer showed the maximum current value.

Next, 10,000 parts by mass of ion-exchanged water at 60℃ was added to the kneaded product for 2 hours to obtain a liquid mixture. The mass ratio of the styrene acrylic resin contained in the liquid mixture to the magenta pigment was 0.29.

Next, ion-exchanged water and triethylene glycol were added to the liquid mixture to obtain a magenta aqueous pigment dispersing liquid having a magenta pigment concentration of 14.5%by mass and a concentration of triethylene glycol of 100%by mass with respect to the magenta pigment.

Then, 5.6 parts by mass of 2-pyrrolidinone (manufactured by BASF SE) , 5.6 parts by mass of triethylene glycol monobutyl ether (manufactured by Tokyo Chemical Industry Co., Ltd. ) , 2.1 parts by mass of purified glycerin (manufactured by Kao Corporation) , 0.3 parts by mass of SURFYNOL 440 (non-ionic surfactant, manufactured by Evonik Japan) , and ion-exchanged water were placed in a plastic container and stirred for 1 hour. And then 1.7 parts by mass of the dispersion (II-1) was added to this solution. The solution was further added to an another plastic container having 14.5 parts by mass of the magenta aqueous pigment dispersing liquid, and stirred for 1 hour.

Then, the pH of the mixture was adjusted to be in the range of 9 to 9.8 using a 5 mass%aqueous potassium hydroxide solution, and the mixture was filtered through a filter having a pore size of 5 to 10 μm to obtain a total of 70 parts by mass of water-based ink M1 (magenta pigment concentration 3%by mass) .

[Example 2]

A water-based ink M2 was obtained by the same method as in Example 1 except that the dispersion (II-2) was used instead of the dispersion (II-1) .

[Example 3]

A water-based ink M3 was obtained by the same method as in Example 1 except that the dispersion (II-3) was used instead of the dispersion (II-1) .

[Example 4]

A water-based ink M4 was obtained by the same method as in Example 1 except that the dispersion (II-4) was used instead of the dispersion (II-1) .

[Example 5]

A water-based ink M5 was obtained by the same method as in Example 1 except that the dispersion (II-5) was used instead of the dispersion (II-1) .

[Example 6]

A water-based ink M6 was obtained by the same method as in Example 1 except that the dispersion (II-6) was used instead of the dispersion (II-1) .

[Example 7]

A water-based ink M7 was obtained by the same method as in Example 1 except that the dispersion (II-7) was used instead of the dispersion (II-1) .

[Example 8]

A water-based ink M8 was obtained by the same method as in Example 1 except that the dispersion (II-8) was used instead of the dispersion (II-1) .

[Example 9]

A water-based ink M9 was obtained by the same method as in Example 1 except that the dispersion (II-9) was used instead of the dispersion (II-1) .

[Example 10]

A water-based ink M10 was obtained by the same method as in Example 1 except that the dispersion (II-10) was used instead of the dispersion (II-1) .

[Comparative Example 1]

A water-based ink M11 was obtained by the same method as in Example 1 except that the dispersion (II-11) was used instead of the dispersion (II-1) .

[Comparative Example 2]

A water-based ink M12 was obtained by the same method as in Example 1 except that the dispersion (II-12) was used instead of the dispersion (II-1) .

[Comparative Example 3]

A water-based ink M13 was obtained by the same method as in Example 1 except that the dispersion (II-13) was used instead of the dispersion (II-1) .

[Comparative Example 4]

A water-based ink M14 was obtained by the same method as in Example 1 except that the dispersion (II-14) was used instead of the dispersion (II-1) .

[Comparative Example 5]

A water-based ink M15 was obtained by the same method as in Example 1 except that the dispersion (II-15) was used instead of the dispersion (II-1) .

[Comparative Example 6]

A water-based ink M16 was obtained by the same method as in Example 1 except that the dispersion (II-16) was used instead of the dispersion (II-1) .

[Comparative Example 7]

A water-based ink M17 was obtained by the same method as in Example 1 except that HYDRAN WLS-210 manufactured by DIC Corporation was used instead of the dispersion (II-1) .

[Comparative Example 8]

A water-based ink M18 was obtained by the same method as in Example 1 except that the dispersion (II-17) was used instead of the dispersion (II-1) .

[Comparative Example 9]

A water-based ink M19 was obtained by the same method as in Example 1 except that the dispersion (II-18) was used instead of the dispersion (II-1) .

[Comparative Example 10]

A water-based ink M20 was obtained by the same method as in Example 1 except that ion-exchanged water was used instead of the dispersion (II-1) .

[Table 3]

[Table 4]

The inks obtained in Examples and Comparative Examples were applied to brochure &flyer paper (double-sided glossy paper) manufactured by HP using bar coater No. 3, and were left in an environment of 25℃ for 60 seconds to dry to obtain the printed papers.

Next, the printed paper was placed and attached on the rubbing area of fastness rubbing tester (RT-300S manufactured by Daiei Kagaku Seiki MFG. Co., Ltd. ) by plastic tape, and the surface of the printed paper was rubbed to-and-fro with a rubbing peg that was covered with another piece of the brochure &flyer paper under the condition of a loading weight of 200 g.

Next, the rubbed surface of the printed paper was scanned and converted into image data, and the number of pixels in the remaining part of the color was counted. Referring to the entire area of the image was counted as 100 pixels, it was determined that the larger the number of pixels in the remaining part of the color is better the rub fastness.

A: The number of pixels in the remaining color part was more than 60.

B: The number of pixels in the remaining color part was 40 or more and 60 or less.

C: The number of pixels in the remaining color part was 20 or more and 40 or less.

D: The number of pixels in the remaining color part was less than 20.

The ink obtained in Comparative Example 10 was filled in an ink cartridge. Next, the ink was printed on an OHP sheet (a sheet with a layer that absorbs ink on the surface of the film) for inkjet with a print density of 100%using a commercially available thermal-jet inkjet printer to obtain a printed matter. After the printed matter was left to dry in an environment of 25℃ for 1 hour, a maximum absorbance (Abs ₀) of the printed matter was measured with an ultraviolet and visible spectrophotometer (JASCO Corporation V-660 type) using the unprinted part of the OHP sheet as a reference.

Next, the inks obtained in Examples 1 to 10 and Comparative Examples 1 to 9 were filled in ink cartridges.

Then, the inks were respectively printed on an OHP sheet for inkjet with a print density of 100%using a commercially available thermal-jet inkjet printer to obtain printed matters. After the printed matters were respectively left to dry in an environment of 25℃ for 1 hour, a maximum absorbance (Abs ₁) of the printed matters was measured with an ultraviolet and visible spectrophotometer (JASCO Corporation V-660 type) using the unprinted part of the OHP sheet as a reference.

Based on the values obtained from the formula [maximum absorbance (Abs ₁) /maximum absorbance (Abs ₀) ] × 100, the discharge properties of the inks were evaluated according to the following criteria.

A: The value of the above formula was 70 or more.

B: The value of the above formula was 60 or more and less than 70.

C: The value of the above formula was 50 or more and less than 60.

D: The value of the above formula was less than 50.

The ink obtained in Comparative Example 10 was applied to commercially available plain paper using bar coater No. 3, dried in an environment of 25℃ for 1 hour, and then the optical density as benchmark (OD ₀) of the printed area was measured by an integrating sphere spectrophotometer X-Rite (X-Rite, Inc. ) .

Next, the inks obtained in Examples 1 to 10 and Comparative Examples 1 to 9 were applied to commercially available plain paper using bar coater No. 3, dried for 1 hour, and then the optical density (OD ₁) of the printed area was respectively measured by an integrating sphere spectrophotometer X-Rite.

Based on the values obtained from the formula [optical density (OD ₁) /optical density (OD ₀) ] × 100, the coloring properties of the printed matters were evaluated according to the following criteria.

A: The value of the above formula was 90 or more.

B: The value of the above formula was 85 or more and less than 90.

C: The value of the above formula was 80 or more and less than 85.

D: The value of the above formula was less than 80.

A 5 cm × 5 cm square cotton cloth was immersed in the ink obtained in Examples and Comparative Examples and was dried at 150℃ for 5 minutes to obtain a test samples. Then, the optical density (OD ₀) of the test samples were measured using an integrating sphere spectrophotometer X-Rite.

Next, the test samples were immersed in a detergent liquid at 50℃ based on JIS L0844: 2011 for 30 minutes, and then the detergent liquid and the test samples were stirred for 1 minute with a food mixer. The samples were washed with water and dried at room temperature. Then, the optical density (OD ₁) of the test samples were measured using an integrating sphere spectrophotometer X-Rite.

Based on the values obtained from the formula [optical density (OD ₁) /optical density (OD ₀) ] × 100, the washing fastness of the printed matters were evaluated according to the following criteria.

A: The value of the above formula was 85 or more.

B: The value of the above formula was 70 or more and less than 85.

C: The value of the above formula was 60 or more and less than 70.

D: The value of the above formula was less than 60.

[Table 5]

(Being better than B is judged to be good. )

[Table 6]

(Being better than B is judged to be good. )

Claims

An ink in which a polymer (B) having an aromatic ring structure is dispersed in water (C) by a polymer (A) having a carboxyl group or a functional group in which a carboxyl group is neutralized by some basic compounds and a structural unit represented by the following general formula (1) .

(M in the general formula (1) represents a hydrogen atom or an alkali metal. )
The ink according to claim 1, wherein the polymer (A) is a polymer of a monomer mixture including a monomer having a carboxyl group or an acid anhydride thereof, and an alkali metal salt of styrene sulfonic acid.
The ink according to claim 1 or 2, wherein the polymer (B) has a structural unit derived from styrene.
The ink according to any one of claims 1 to 3, wherein a mass ratio of the polymer (A) to the polymer (B) [polymer (A) /polymer (B) ] is in a range of 1/100 to 30/100.
The ink according to any one of claims 1 to 4, wherein the polymer (A) and the polymer (B) are contained in a total amount in a range of 0.1%by mass to 30%by mass, based on the total amount of the ink.
The ink according to any one of claims 1 to 5, wherein a dispersion, in which the polymer (B) is dispersed in water (C) by the polymer (A) , has a volume average particle size of 20 nm to 1000 nm.
The ink according to any one of claims 1 to 6, further including a pigment and a pigment-dispersing resin for dispersing the pigment in the water (C) .
The ink according to any one of claims 1 to 7, which is used for printing in an inkjet printing method.
The ink according to claim 8, wherein the inkjet printing method is a thermal type inkjet printing method.